Electrolytic solution and electrochemical device

ABSTRACT

One aspect of the present invention provides an electrolytic solution comprising a compound represented by the following formula (1), wherein a content of the compound is 10% by mass or less based on the total amount of the electrolytic solution, 
     
       
         
         
             
             
         
       
     
     wherein R 1  to R 3  each independently represent an alkyl group or a fluorine atom, R 4  represents an alkylene group, and R 5  represents an organic group containing a nitrogen atom.

TECHNICAL FIELD

The present invention relates to an electrolytic solution and anelectrochemical device.

BACKGROUND ART

In recent years, high-performance electrochemical devices are neededsuch as non-aqueous electrolytic solution secondary batteries,representative examples including lithium ion secondary batteries, andcapacitors, due to the widespread use of portable electronic devices andelectric vehicles. As means for improving the performance of anelectrochemical device, for example, a method of adding a predeterminedadditive to an electrolytic solution has been studied. In PatentLiterature 1, there is disclosed an electrolytic solution for anon-aqueous electrolytic solution battery which contains a specificsiloxane compound in order to improve cycle characteristics and internalresistance characteristics.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Unexamined Patent Publication No.2015-005329

SUMMARY OF INVENTION Technical Problem

As is described in Patent Literature 1, it is important to reduce aresistance of the electrochemical device. Then, an object of thisinvention is to provide an electrolytic solution that can reduce theresistance of the electrochemical device. In addition, another object ofthe present invention is to provide an electrochemical device having areduced resistance.

Solution to Problem

The present inventors have found that the resistance of theelectrochemical device can be reduced by the specific compoundcontaining silicon atoms and nitrogen atoms being contained in theelectrolytic solution.

In addition, as one of the other characteristics which are required forelectrochemical devices, low-temperature input characteristics areincluded. The charging capacity of the electrochemical device decreasesat low temperature (for example, 0° C. or lower) than the chargingcapacity at normal temperature (for example, 25° C.), but it is alsorequired for the electrochemical devices to suppress the decrease of thecharging capacity as much as possible, in other words, to be excellentin the low-temperature input characteristics. The present inventors havealso found that the low-temperature input characteristics of theelectrochemical device can be improved by the specific compoundcontaining silicon atoms and nitrogen atoms being contained in theelectrolytic solution.

In addition, as is described in Patent Literature 1, it is alsoimportant to improve cycle characteristics of the electrochemicaldevice. In addition, it is also important to improve discharge ratecharacteristics of the electrochemical device. Furthermore, it is alsorequired that the volume increase (expansion) of the electrochemicaldevice with time is suppressed. It has also been found by the presentinventors that these characteristics of the electrochemical device canbe improved by the compound being contained in the electrolyticsolution.

The present invention provides, as a first aspect, an electrolyticsolution comprising a compound represented by the following formula (1),wherein a content of the compound is 10% by mass or less based on thetotal amount of the electrolytic solution,

wherein R¹ to R³ each independently represent an alkyl group or afluorine atom, R⁴ represents an alkylene group, and R⁵ represents anorganic group containing a nitrogen atom.

R⁵ is preferably a group represented by the following formula (2):

wherein R⁶ and R⁷ each independently represent a hydrogen atom or analkyl group, and * represents a bond.

At least one of R¹ to R³ is preferably a fluorine atom.

The present invention provides, as a second aspect, an electrochemicaldevice comprising a positive electrode, a negative electrode and theabove electrolytic solution.

The negative electrode preferably comprises a carbon material. Thecarbon material preferably comprises graphite. The negative electrodepreferably further comprises a material comprising at least one elementof the group consisting of silicon and tin.

The electrochemical device is preferably a non-aqueous electrolyticsolution secondary battery or a capacitor.

Advantageous Effects of Invention

According to the present invention, an electrolytic solution that canreduce a resistance of an electrochemical device can be provided. Inaddition, according to the present invention, an electrochemical devicehaving a reduced resistance can be provided. In addition, according toone aspect of the present invention, it is also possible to provide anelectrolytic solution that can improve low-temperature inputcharacteristics and/or cycle characteristics of an electrochemicaldevice, and an electrochemical device that is excellent in thelow-temperature input characteristics and/or the cycle characteristics.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a perspective view showing a non-aqueous electrolyticsolution secondary battery which is an electrochemical device accordingto one embodiment.

FIG. 2 shows an exploded perspective view showing an electrode group ofthe secondary battery shown in FIG. 1.

FIG. 3 shows a graph showing measurement results of resistances inExample 1 and Comparative Example 1.

FIG. 4 shows a graph showing measurement results of resistances inExamples 2 to 4 and Comparative Examples 2 to 3.

FIG. 5 shows a graph showing evaluation results of cycle characteristicsof Example 2 and Comparative Examples 2 to 3.

FIG. 6 shows a graph showing measurement results of resistances (atupper limit voltage of 4.2 V) in Examples 5 to 6 and Comparative Example4.

FIG. 7 shows a graph showing measurement results of resistances (atupper limit voltage of 4.3 V) in Example 5 and Comparative Example 4.

FIG. 8 shows a graph showing measurement results of resistances inExamples 7 to 8 and Comparative Example 5.

FIG. 9 shows a graph showing measurement results of resistances inExamples 9 to 10 and Comparative Example 6.

FIG. 10 shows a graph showing measurement results of resistances inExamples 11 to 12 and Comparative Example 7.

FIG. 11 shows a graph showing measurement results of resistances inExample 13 and Comparative Example 8.

FIG. 12 shows a graph showing evaluation results of cyclecharacteristics of Example 14 and Comparative Example 8.

FIG. 13 shows a graph showing evaluation results of discharge ratecharacteristics of Example 13 and Comparative Example 8.

FIG. 14 shows a graph showing measurement results of resistances inExample 15 and Comparative Examples 9 to 10.

FIG. 15 shows a graph showing measurement results of amounts of volumechanges in Example 15 and Comparative Examples 9 to 10.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described below,appropriately referring to the drawings. However, the present inventionis not limited to the following embodiments.

FIG. 1 shows a perspective view showing an electrochemical deviceaccording to one embodiment. In the present embodiment, theelectrochemical device is a non-aqueous electrolytic solution secondarybattery. As shown in FIG. 1, the non-aqueous electrolytic solutionsecondary battery 1 comprises: an electrode group 2 including a positiveelectrode, a negative electrode and a separator; and a bag-shapedbattery outer package 3 which accommodates the electrode group 2. Apositive electrode current collector tab 4 and a negative electrodecurrent collector tab 5 are provided on the positive electrode and thenegative electrode, respectively. The positive electrode currentcollector tab 4 and the negative electrode current collector tab 5protrude from the inside of the battery outer package 3 to the outsideso that the positive electrode and the negative electrode can beelectrically connected to the outside of the non-aqueous electrolyticsolution secondary battery 1, respectively. The battery outer package 3is filled with an electrolytic solution (not illustrated). Thenon-aqueous electrolytic solution secondary battery 1 may be a batteryhaving another shape (coin type, cylindrical type, layered type and thelike) than that of the so-called “laminate type” as described above.

The battery outer package 3 may be a container which is formed of, forexample, a laminate film. The laminate film may be, for example, alaminated film in which a resin film such as a polyethyleneterephthalate (PET) film, a foil of metal such as aluminum, copper andstainless steel, and a sealant layer made from polypropylene or the likeare laminated in this order.

FIG. 2 shows an exploded perspective view showing one embodiment of theelectrode group 2 in the non-aqueous electrolytic solution secondarybattery 1 shown in FIG. 1. As shown in FIG. 2, the electrode group 2 hasa positive electrode 6, a separator 7 and a negative electrode 8, inthis order. The positive electrode 6 and the negative electrode 8 arearranged so that a positive electrode mixture layer 10 side and anegative electrode mixture layer 12 side face the separator 7,respectively.

The positive electrode 6 has a positive electrode current collector 9,and a positive electrode mixture layer 10 provided on the positiveelectrode current collector 9. The positive electrode current collector9 is provided with the positive electrode current collector tab 4.

The positive electrode current collector 9 is formed from, for example,aluminum, titanium, stainless steel, nickel, baked carbon, anelectroconductive polymer, or electroconductive glass. The positiveelectrode current collector 9 may have a surface of aluminum, copper orthe like which has been treated with carbon, nickel, titanium, silver orthe like, for the purpose of improving adhesiveness, electroconductivityand oxidation resistance. The thickness of the positive electrodecurrent collector 9 is, for example, 1 to 50 μm from the viewpoint ofelectrode strength and energy density.

In one embodiment, the positive electrode mixture layer 10 contains apositive electrode active material, an electroconductive agent, and abinder. The thickness of the positive electrode mixture layer 10 is, forexample, 20 to 200 μm.

The positive electrode active material may be, for example, lithiumoxide. Examples of the lithium oxide include Li_(x)CoO₂, Li_(x)NiO₂,Li_(x)MnO₂, Li_(x)Co_(y)Ni_(1-y)O₂, Li_(x)Co_(y)M_(1-y)O_(z),Li_(x)Ni_(1-y)M_(y)O_(z), Li_(x)Mn₂O₄ and Li_(x)Mn_(2-y)M_(y)O₄ (whereinin each formula, M represents at least one element selected from thegroup consisting of Na, Mg, Sc, Y, Mn, Fe, Co, Cu, Zn, Al, Cr, Pb, Sb, Vand B (provided that M is an element different from the other elementsin each formula); and x=0 to 1.2, y=0 to 0.9, and z=2.0 to 2.3). Thelithium oxide represented by Li_(x)Ni_(1-y)M_(y)O_(z) may beLi_(x)Ni_(1−(y1+y2)) CO_(y1)Mn_(y2)O_(z) (provided that x and z are thesame as those described above, and y1=0 to 0.9, y2=0 to 0.9, and y1+y2=0to 0.9), and may be, for example, LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂,LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂, LiNi_(0.6)Co_(0.2)Mn_(0.2)O₂ andLiNi_(0.8)Co_(0.1)Mn_(0.1)O₂. The lithium oxide represented byLi_(x)Ni_(1-y)M_(y)O_(z) may be Li_(x)Ni_(1−(y3+y4))Co_(y3)Al_(y4)O(provided that x and z are the same as those described above, and y3=0to 0.9, y4=0 to 0.9, and y3+y4=0 to 0.9), and may be, for example,LiNi_(0.8)Co_(0.15)Al_(0.05)O₂.

The positive electrode active material may be, for example, lithiumphosphate. Examples of the lithium phosphate include lithium manganesephosphate (LiMnPO₄), lithium iron phosphate (LiFePO₄), lithium cobaltphosphate (LiCoPO₄), and lithium vanadium phosphate (Li₃V₂(PO₄)₃).

The content of the positive electrode active material may be 80% by massor more, or 85% by mass or more based on the total amount of thepositive electrode mixture layer, and 99% by mass or less.

The electroconductive agent may be carbon black such as acetylene blackor ketjen black, a carbon material such as graphite or graphene, acarbon nanotube, or the like. The content of the electroconductive agentmay be, for example, 0.01% by mass or more, 0.1% by mass or more, or 1%by mass or more based on the total amount of the positive electrodemixture layer, and may be 50% by mass or less, 30% by mass, or 15% bymass or less.

Examples of the binder include: resins such as polyethylene,polypropylene, polyethylene terephthalate, polymethyl methacrylate,polyimide, aromatic polyamide, cellulose and nitrocellulose; rubberssuch as SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadienerubber), fluorine rubber, isoprene rubber, butadiene rubber andethylene-propylene rubber; thermoplastic elastomers such asstyrene/butadiene/styrene block copolymers or hydrogenated productsthereof, EPDM (ethylene/propylene/diene terpolymer),styrene/ethylene/butadiene/ethylene copolymers, andstyrene/isoprene/styrene block copolymers or hydrogenated productsthereof; soft resins such as syndiotactic-1,2-polybutadiene, polyvinylacetate, ethylene/vinyl acetate copolymers, and propylene α-olefincopolymers; fluorine-containing resins such as polyvinylidene fluoride(PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride,polytetrafluoroethylene/ethylene copolymers,polytetrafluoroethylene/vinylidene fluoride copolymers; resins having anitrile group-containing monomer as a monomer unit; and polymercompositions having an ion conductivity of an alkali metal ion (forexample, lithium ion).

The content of the binder may be, for example, 0.1% by mass or more, 1%by mass or more, or 1.5% by mass or more based on the total amount ofthe positive electrode mixture layer, and may be 30% by mass or less,20% by mass or less, or 10% by mass or less.

The separator 7 is not limited in particular as long as the separatorelectronically insulates between the positive electrode 6 and thenegative electrode 8, and on the other hand, allows ions to passtherethrough, and has resistances to an oxidizing property in thepositive electrode 6 side and to a reducing property in the negativeelectrode 8 side. Examples of the material (quality of material) of theseparator 7 include resins and inorganic substances.

The resins include olefin-based polymers, fluorine-based polymers,cellulose-based polymers, polyimide and nylon. The separator 7 ispreferably a porous sheet or a nonwoven fabric which is formed from apolyolefin such as polyethylene and polypropylene, from the viewpoint ofbeing stable with respect to the electrolytic solution and excellent inliquid retentivity.

The inorganic substances include: oxides such as alumina and silicondioxide; nitrides such as aluminum nitride and silicon nitride; andsulfates such as barium sulfate and calcium sulfate. The separator 7 maybe, for example, a separator in which a fibrous or particulate inorganicsubstance is bonded to a thin film substrate such as a nonwoven fabric,a woven fabric and a microporous film.

The negative electrode 8 has a negative electrode current collector 11,and a negative electrode mixture layer 12 provided on the negativeelectrode current collector 11. The negative electrode current collector11 is provided with a negative electrode current collector tab 5.

The negative electrode current collector 11 is formed from copper,stainless steel, nickel, aluminum, titanium, baked carbon, anelectroconductive polymer, electroconductive glass, an aluminum-cadmiumalloy, or the like. The negative electrode current collector 11 may beone in which the surface of copper, aluminum or the like is treated withcarbon, nickel, titanium, silver or the like, for the purpose ofimproving adhesiveness, electroconductivity, and resistance toreduction. The thickness of the negative electrode current collector 11is, for example, 1 to 50 μm, from the viewpoint of the electrodestrength and the energy density.

The negative electrode mixture layer 12 contains, for example, anegative electrode active material and a binder.

The negative electrode active material is not limited in particular aslong as the active material is a material which can occlude and releaselithium ions. Examples of the negative electrode active materialinclude: carbon materials; metal composite oxides; oxides or nitrides ofGroup 4 elements such as tin, germanium and silicon; a simple substanceof lithium; lithium alloys such as lithium aluminum alloys; and metalswhich can form an alloy with lithium, such as Sn and Si. The negativeelectrode active material is preferably at least one selected from thegroup consisting of the carbon material and the metal composite oxide,from the viewpoint of safety. The negative electrode active material maybe one type alone or a mixture of two or more of the materials. Theshape of the negative electrode active material may be, for example, aparticulate shape.

The carbon materials include: amorphous carbon materials; naturalgraphite; composite carbon materials in which a film of amorphous carbonmaterial is formed on natural graphite; and artificial graphite (onethat is obtained by baking raw materials of resins such as epoxy resinand phenol resin, or pitch-based raw materials which are obtained frompetroleum, coal and the like). The metal composite oxide preferablycontains one or both of titanium and lithium, and more preferablycontains lithium, from the viewpoint of charge/discharge characteristicsat high current density.

Among the negative electrode active materials, the carbon materials havehigh electroconductivity, and are particularly excellent in lowtemperature characteristics and cycle stability. Among the carbonmaterials, the graphite is preferable from the viewpoint of increasingthe capacity. In graphite, the interlayer spacing (d002) between carbonnetwork planes in the X-ray wide angle diffraction method is preferablysmaller than 0.34 nm, and is more preferably 0.3354 nm or larger and0.337 nm or smaller. A carbon material which satisfies such conditionsis referred to as pseudo-anisotropic carbon, in some cases.

The negative electrode active material may further include a materialcontaining at least one element selected from the group consisting ofsilicon and tin. The material containing at least one element selectedfrom the group consisting of silicon and tin may be a compoundcontaining at least one element selected from the group consisting of asimple substance of silicon or tin, silicon and tin. The compound may bean alloy containing at least one element selected from the groupconsisting of silicon and tin, and is, for example, an alloy containingat least one selected from the group consisting of nickel, copper, iron,cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth,antimony and chromium, in addition to silicon and tin. The compoundcontaining at least one element selected from the group consisting ofsilicon and tin may be an oxide, a nitride or a carbide, andspecifically may be, for example, a silicon oxide such as SiO, SiO₂ andLiSiO, a silicon nitride such as Si₃N₄ and Si₂N₂O, a silicon carbidesuch as SiC, and a tin oxide such as SnO, SnO₂ and LiSnO.

The negative electrode 8 preferably contains a carbon material as anegative electrode active material, more preferably contains graphite,and further preferably contains a mixture of a carbon material and amaterial containing at least one element selected from the groupconsisting of silicon and tin, and particularly preferably contains amixture of graphite and silicon oxide, from the viewpoint of furtherimproving the low-temperature input characteristics of theelectrochemical device. The content of the carbon material (graphite) inthe mixture relative to the material containing at least one elementselected from the group consisting of silicon and tin (silicon oxide)may be 1% by mass or more, or 3% by mass or more, and may be 30% by massor less, based on the total amount of the mixture.

The content of the negative electrode active material may be 80% by massor more or 85% by mass or more, and may be 99% by mass or less, based onthe total amount of the negative electrode mixture layer.

The binder and its content may be the same as the binder and its contentin the positive electrode mixture layer described above.

The negative electrode mixture layer 12 may contain a thickening agentin order to adjust the viscosity. The thickening agent is not limited inparticular, and may be carboxymethyl cellulose, methyl cellulose,hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidizedstarch, phosphorylated starch, casein, and salts thereof, and the like.The thickening agent may be one type alone or a mixture of two or moreof the materials.

In the case where the negative electrode mixture layer 12 contains thethickening agent, the content is not limited in particular. The contentof the thickening agent may be 0.1% by mass or more, is preferably 0.2%by mass or more, and is more preferably 0.5% by mass or more, based onthe total amount of the negative electrode mixture layer, from theviewpoint of coating properties of the negative electrode mixture layer.The content of the thickening agent may be 5% by mass or less, ispreferably 3% by mass or less, and is more preferably 2% by mass orless, based on the total amount of the positive electrode mixture layer,from the viewpoint of suppressing a decrease in battery capacity or anincrease in resistance between the negative electrode active materials.

In one embodiment, the electrolytic solution contains a compoundrepresented by the following formula (1), an electrolyte salt and anon-aqueous solvent,

wherein R¹ to R³ each independently represent an alkyl group or afluorine atom, R⁴ represents an alkylene group, and R⁵ represents anorganic group containing a nitrogen atom.

The number of carbon atoms of the alkyl group represented by R¹ to R³may be 1 or more and 3 or less. R¹ to R³ may be a methyl group, an ethylgroup or a propyl group, and may be any of a straight-chain group and abranched-chain group. At least one of R¹ to R³ is preferably a fluorineatom.

The number of carbon atoms of the alkylene group represented by R⁴ maybe 1 or more, or 2 or more, and 5 or less, or 4 or less. The alkylenegroup represented by R⁴ may be a methylene group, an ethylene group, apropylene group, a butylene group or a pentylene group, and may be anyof a straight-chain group and a branched-chain group.

R⁵ may be a group represented by the following formula (2) in oneembodiment, from the viewpoint of further reducing the resistance of theelectrochemical device and further improving the low-temperature inputcharacteristics,

wherein R⁶ and R⁷ each independently represent a hydrogen atom or analkyl group. The alkyl group represented by R⁶ or R⁷ may be the same asthe alkyl group represented by R¹ to R³ described above; and *represents a bond.

In one embodiment, the number of silicon atoms in one molecule of thecompound represented by the formula (1) is one. In other words, in oneembodiment, an organic group represented by R⁵ does not contain asilicon atom.

The content of the compound represented by the formula (1) is preferably0.001% by mass or more, based on the total amount of the electrolyticsolution, and is more preferably 0.005% by mass or more, and is furtherpreferably 0.01% by mass or more, from the viewpoint of further reducingthe resistance of the electrochemical device and further improving thelow-temperature input characteristics. From the same viewpoint, thecontent of the compound represented by the formula (1) is preferably 10%by mass or less, 7% by mass or less, 5% by mass or less, 3% by mass orless, 2% by mass or less, 1.5% by mass or less, or 1% by mass or less,based on the total amount of the electrolytic solution. The content ofthe compound represented by the formula (1) is preferably 0.001 to 10%by mass, 0.001 to 7% by mass, 0.001 to 5% by mass, 0.001 to 3% by mass,0.001 to 2% by mass, 0.001 to 1.5% by mass, 0.001 to 1% by mass, 0.005to 10% by mass, 0.005 to 7% by mass, 0.005 to 5% by mass, 0.005 to 3% bymass, 0.005 to 2% by mass, 0.005 to 1.5% by mass, 0.005 to 1% by mass,0.01 to 10% by mass, 0.01 to 7% by mass, 0.01 to 5% by mass, 0.01 to 3%by mass, 0.01 to 2% by mass, 0.01 to 1.5% by mass, or 0.01 to 1% bymass, based on the total amount of the electrolytic solution, from theviewpoint of further improving the low-temperature input characteristicsof the electrochemical device.

The electrolyte salt may be a lithium salt, for example.

Examples of the lithium salt may be at least one selected from the groupconsisting of LiPF₆, LiBF₄, LiClO₄, LiB(C₆H₅)₄, LiCH₃SO₃, CF₃SO₂OLi,LiN(SO₂F)₂ (Li[FSI], lithium bis(fluorosulfonyl)imide),LiN(SO₂CF₃)₂(Li[TFSI], lithium bis(trifluoromethane sulfonyl)imide), andLiN(SO₂CF₂CF₃)₂. The lithium salt preferably contains LiPF₆, from theviewpoint of further being excellent in solubility to a solvent,charge/discharge characteristics of a secondary battery, outputcharacteristics, cycle characteristics and the like.

The concentration of the electrolyte salt is preferably 0.5 mol/L orhigher, more preferably 0.7 mol/L or higher, further preferably 0.8mol/L or higher, based on the total amount of the non-aqueous solvent,and is preferably 1.5 mol/L or lower, more preferably 1.3 mol/L orlower, and further preferably 1.2 mol/L or lower, from the viewpoint ofexcellent charge/discharge characteristics.

The examples of the non-aqueous solvent include ethylene carbonate,propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethylcarbonate, γ-butyl lactone, acetonitrile, 1,2-dimethoxyethane,dimethoxymethane, tetrahydrofuran, dioxolane, methylene chloride, andmethyl acetate. The non-aqueous solvent may be one type alone or amixture of two or more of these solvents, and is preferably the mixtureof two or more.

The electrolytic solution may further contain other materials than thecompound represented by the formula (1), the electrolyte salt and thesolvent. Other materials may be, for example, a heterocyclic compoundcontaining nitrogen, sulfur, or nitrogen and sulfur, a cyclic carboxylicacid ester, a fluorine-containing cyclic carbonate, other compoundshaving an unsaturated bond in a molecule, or the like.

The present inventors have studied compounds which have variousstructures and functional groups, and as a result, have revealed thatthe low-temperature input characteristics have been remarkably improvedand the resistance has been reduced by applying the compound representedby the above formula (1) to the electrolytic solution. The presentinventors assume the effects of using the compound represented by theformula (1) in the electrolytic solution to be as follows. The compoundrepresented by the formula (1) forms a stable film on the positiveelectrode or the negative electrode. Thereby, the lowering of the outputcharacteristics at the low temperature is suppressed, which originatesin the deposition of a decomposed product of the electrolytic solutionon the positive electrode or the negative electrode. Furthermore, thelowering of the capacity at the low temperature and the increase of theresistance are suppressed, which originate in the decomposition of theelectrolyte salt. As a result, the low-temperature input characteristicsof the non-aqueous electrolytic solution secondary battery 1 areimproved. Furthermore, the compound represented by the formula (1)itself has a skeleton containing Si, and thereby generation of gasderived from the compound is reduced, and the volume expansion can besuppressed which occurs when the non-aqueous electrolytic solutionsecondary battery 1 is stored at high temperature.

Subsequently, a method for manufacturing the non-aqueous electrolyticsolution secondary battery 1 will be described. The method formanufacturing the non-aqueous electrolytic solution secondary battery 1includes: a first step of obtaining the positive electrode 6; a secondstep of obtaining the negative electrode 8; a third step ofaccommodating the electrode group 2 in the battery outer package 3; anda fourth step of injecting an electrolytic solution into the batteryouter package 3.

In the first step, the positive electrode 6 is obtained by: dispersing amaterial to be used for the positive electrode mixture layer 10 in adispersion medium by using a kneader, a disperser or the like to obtaina slurry-like positive electrode mixture; then applying the positiveelectrode mixture onto the positive electrode current collector 9 by adoctor blade method, a dipping method, a spray method or the like; andthen volatilizing the dispersion medium. After volatilization of thedispersion medium, a step of compression molding using a roll press maybe provided as needed. The above steps from the application of thepositive electrode mixture to the volatilization of the dispersionmedium may be performed a plurality of times, and thereby the positiveelectrode mixture layer 10 may be formed as a positive electrode mixturelayer having a multilayer structure. The dispersion medium may be water,1-methyl-2-pyrrolidone (hereinafter also referred to as NMP), or thelike.

The second step may be the same step as the first step described above,and the method of forming the negative electrode mixture layer 12 on thenegative electrode current collector 11 may be the same method as thefirst step described above.

In the third step, the separator 7 is sandwiched between the producedpositive electrode 6 and negative electrode 8, and the electrode group 2is formed. Next, the electrode group 2 is accommodated in the batteryouter package 3.

In the fourth step, the electrolytic solution is injected into thebattery outer package 3. The electrolytic solution can be prepared, forexample, by firstly dissolving an electrolyte salt in a solvent, andthen dissolving other materials thereinto.

As for another embodiment, the electrochemical device may be acapacitor. The capacitor may include, similarly to the non-aqueouselectrolytic solution secondary battery 1 described above, the electrodegroup including the positive electrode, the negative electrode and theseparator, and a bag-shaped battery outer package which accommodates theelectrode group. The details of each component in the capacitor may bethe same as those of the non-aqueous electrolytic solution secondarybattery 1.

EXAMPLES

The present invention will be specifically described below withreference to Examples, but the present invention is not limited to theseExamples.

Example 1

[Production of Positive Electrode]

Fibrous graphite (1% by mass) and acetylene black (AB) (1% by mass) ofelectroconductive agents, and a binder (3% by mass) were sequentiallyadded to and mixed with lithium cobaltate (95% by mass) of a positiveelectrode active material. To the obtained mixture, NMP of a dispersionmedium was added, the resultant mixture was kneaded, and thereby aslurry-like positive electrode mixture was prepared. A predeterminedamount of this positive electrode mixture was evenly and uniformlyapplied to an aluminum foil which was a positive electrode currentcollector and had a thickness of 20 μm. After that, the dispersionmedium was volatilized, then the resultant mixture was compressed to adensity of 3.6 g/cm³ by pressing, and a positive electrode was obtained.

[Production of Negative Electrode]

A binder and carboxymethylcellulose of a thickening agent were added tographite of a negative electrode active material. Mass ratios among thematerials were set to be negative electrode activematerial:binder:thickening agent=98:1:1. To the obtained mixture, waterwas added as a dispersion medium, and the mixture was kneaded to preparea slurry-like negative electrode mixture. A predetermined amount of thisnegative electrode mixture was evenly and uniformly applied to a rolledcopper foil which was a negative electrode current collector and had athickness of 10 μm. After that, the dispersion medium was volatilized,then the resultant mixture was compressed to a density of 1.6 g/cm³ bypressing, and a negative electrode was obtained.

[Production of Lithium Ion Secondary Battery]

The positive electrode which was cut into a 13.5 cm² square wassandwiched by polyethylene porous sheets (trade name: Hypore (registeredtrademark), manufactured by Asahi Kasei Corporation and thickness of 30μm) which were separators; then, the negative electrode which was cutinto a 14.3 cm² square was further overlapped thereon; and an electrodegroup was produced. This electrode group was accommodated in a container(battery outer package) formed of a laminate film made from aluminum(trade name: aluminum laminate film, manufactured by Dai Nippon PrintingCo., Ltd.). Subsequently, 1 mL of an electrolytic solution was addedinto the container, the container was heat-welded, and the lithium ionsecondary battery for evaluation was produced. As the electrolyticsolution, a solution was used which was prepared by adding 1% by mass ofvinylene carbonate (VC) with respect to the total amount of thefollowing mixed solution, and 1% by mass (based on the total amount ofelectrolytic solution) of the compound A which was represented by thefollowing formula (3), based on the total amount of the electrolyticsolution, into the mixed solution which contained ethylene carbonatecontaining 1 mol/L of LiPF₆, dimethyl carbonate and diethyl carbonate.

Comparative Example 1

A lithium ion secondary battery was produced in the same manner as inExample 1, except that the compound A was not used in Example 1.

[Initial Charge/Discharge]

The produced lithium ion battery was subjected to the initialcharge/discharge by the following method. Firstly, constant currentcharge was performed up to an upper limit voltage of 4.2 V at a currentvalue of 0.1 C in an environment of 25° C., and then constant-voltagecharge was performed at 4.2 V. The charge termination condition was setat a current value of 0.01 C. After that, constant current discharge wasperformed at a current value of 0.1 C to a final voltage of 2.5 V. Thischarge/discharge cycle was repeated three times (“C” used as a unit ofcurrent value means “current value (A)/battery capacity (Ah)”).

[Resistance Measurement by AC Impedance Measurement (Upper Limit Voltageof 4.2 V)]

After the initial charge/discharge, the resistances of the lithium ionsecondary batteries of Example 1 and Comparative Example 1 wereevaluated by AC impedance measurement. The produced lithium ionbatteries were subjected to the constant current charge at a currentvalue of 0.1 C in an environment of 25° C. up to the upper limit voltageof 4.2 V, and were each subsequently subjected to the constant-voltagecharge at 4.2 V. The charge termination condition was set at a currentvalue of 0.01 C. Resistances of these lithium ion secondary batterieswere measured with the use of an AC impedance measuring device (1260type, manufactured by Solartron Analytical) in a frequency range of 20mHz to 200 kHz with an amplitude of 10 mV in an environment of 25° C.The measurement results are shown in FIG. 3.

[Evaluation of Low-Temperature Input Characteristics]

After the initial charge/discharge, the low-temperature inputcharacteristics of each of the secondary batteries of Example 1 andComparative Example 1 were evaluated. Specifically, firstly, constantcurrent charge at 0.1 C was performed up to the upper limit voltage of4.2 V in an environment of 25° C. The capacity at the time of thischarging was defined to be a charging capacity C1 at 25° C. Next, theconstant current discharge was performed at a current value of 0.1 C toa final voltage of 2.5 V in an environment of 25° C. After that, thesamples were held for 1 hour in an environment of −10° C., and then, inthe state of −10° C., were subjected to constant current charge at 0.1 Cup to the upper limit voltage of 4.2 V. The charging capacity at thetime of this charging was defined to be a charging capacity C2 at a lowtemperature (−10° C.). Then, the low-temperature input characteristicswere computed according to the following expression. The results areshown in Table 1.

Low-temperature input characteristics (%)=C2/C1×100

TABLE 1 Example 1 Comparative Example 1 Low-temperature input 80.7 76.4characteristics (%)

Example 2

A lithium ion secondary battery was produced in the same manner as inExample 1, except that silicon oxide was further added as the negativeelectrode active material in Example 1, and the negative electrode wasproduced. Mass ratios among the negative electrode active material, thebinder and the thickening agent in the negative electrode were set to begraphite:siliconoxide:binder:thickening agent=92:5:1.5:1.5.

Examples 3 to 4

Lithium ion secondary batteries were produced in the same manner as inExample 2, except that the contents of the compound A in Example 2 werechanged to 0.5% by mass (Example 3) and 0.1% by mass (Example 4),respectively, based on the total amount of the electrolytic solution.

Comparative Example 2

A lithium ion secondary battery was produced in the same manner as inExample 2, except that the compound A was not used in Example 2.

Comparative Example 3

A lithium ion secondary battery was produced in the same manner as inExample 2, except that 4-fluoro-1,3-dioxolan-2-one (fluoroethylenecarbonate; FEC) instead of the compound A in Example 2 was added in anamount of 1% by mass based on the total amount of the electrolyticsolution.

[Initial Charge/Discharge]

Each of the secondary batteries of Examples 2 to 4 and ComparativeExamples 2 to 3 was subjected to the initial charge/discharge by thesame method as the method in Example 1 and Comparative Example 1.

[Resistance Measurement by AC Impedance Measurement (Upper Limit Voltageof 4.2 V)]

The resistance of each of the secondary batteries of Examples 2 to 4 andComparative Examples 2 to 3 was measured by the same method as in theevaluations in Example 1 and Comparative Example 1. The results areshown in FIG. 4.

[Evaluation of Cycle Characteristics]

The cycle characteristics of each of the secondary batteries in Example2 and Comparative Examples 2 to 3 were evaluated by a cycle test inwhich charge/discharge was repeated after the initial charge/discharge.As for a charging pattern, the secondary batteries of Example 2 andComparative Examples 2 to 3 were subjected to the constant currentcharge at a current value of 0.5 C up to an upper limit voltage of 4.2V, and then were subjected to the constant-voltage charge at 4.2 V, inan environment of 45° C. The charge termination condition was set at acurrent value of 0.05 C. As for discharge, the constant currentdischarge was performed at 1 C up to 2.5 V, and the discharge capacitywas determined. This series of charge/discharge was repeated 200 cycles,and the discharge capacity was measured each time of thecharge/discharge. The discharge capacity after the charge/discharge inthe first cycle in Comparative Example 2 was determined to be 1, andrelative values of the discharge capacities (ratio of dischargecapacity) in Example 2 and Comparative Example 3 in each cycle weredetermined. FIG. 5 shows the relationship between the number of cyclesand the relative values of the discharge capacities.

[Evaluation of Low-Temperature Input Characteristics]

The low-temperature input characteristics of each of the secondarybatteries of Examples 2 to 4 and Comparative Example 2 were evaluated bythe same method as in the evaluations in Example 1 and ComparativeExample 1. The results are shown in Table 2.

TABLE 2 Exam- Exam- Exam- Comparative ple 2 ple 3 ple 4 Example 2Low-temperature input 77.1 77.1 76.6 75.9 characteristics (%)

As shown in FIG. 3 and Table 1, in the lithium ion secondary battery ofExample 1, in which graphite was used as the negative electrode activematerial, and furthermore, to which an electrolytic solution containing1% by mass of the compound A was applied, the resistance was reduced andinput characteristics at low temperature (−10° C.) were satisfactory, ascompared with the lithium ion secondary battery of Comparative Example1, to which an electrolytic solution containing no compound A wasapplied. In addition, as shown in FIG. 4 and Table 2, in the lithium ionsecondary batteries of Examples 2 to 4, in which a negative electrodeactive material containing graphite and silicon oxide was used, andfurthermore, to which electrolytic solutions containing the compound Arespectively in amounts of 1, 0.5 and 0.1% by mass were applied, theresistance was reduced and the input characteristics at low temperature(−10° C.) were satisfactory, as compared with a lithium ion secondarybattery of Comparative Example 2 containing no compound A. The mechanismby which these characteristics were improved is not necessarily clear,but the reason is considered to be because the film was formed on thepositive or negative electrode by the addition of the compound A, thefilm being stable and having a satisfactory ion-conductivity, andbecause by the interaction between the compound A and the lithium ion,the lithium salt (LIPF₆) was stabilized, or activation energy fordesolvation of lithium decreased.

As shown in FIG. 5, in the lithium ion secondary battery of Example 2,in which a negative electrode active material containing graphite andsilicon oxide was used, and furthermore, to which an electrolyticsolution containing 1% by mass of the compound A was applied, cyclecharacteristics were satisfactory, as compared with the lithium ionsecondary batteries of Comparative Examples 2 to 3, which did notcontain the compound A. The mechanism by which these cyclecharacteristics were improved is not necessarily clear, but the reasonis considered to be because the film was formed by the addition of thecompound A, the film being more stable on the positive or negativeelectrode than the film which is formed due to the influence of FEC, andhaving a more satisfactory ion-conductivity, and because thus formedfilm contributed to the suppression of the decomposition of theelectrolytic solution and further to the stabilization of the lithiumsalt (LIPF₆).

Example 5

[Production of Positive Electrode]

Acetylene black (AB) (5% by mass) of the electroconductive agent, and abinder (4% by mass) were sequentially added to and mixed with lithiumnickel cobalt manganate (LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂, 91% by mass) of apositive electrode active material. To the obtained mixture, NMP of adispersion medium was added, the resultant mixture was kneaded, andthereby a slurry-like positive electrode mixture was prepared. Apredetermined amount of this positive electrode mixture was evenly anduniformly applied to an aluminum foil which was a positive electrodecurrent collector and had a thickness of 20 μm. After that, thedispersion medium was volatilized, then the resultant mixture wascompressed to a density of 2.8 g/cm³ by pressing, and a positiveelectrode was obtained.

[Production of Negative Electrode]

A negative electrode was obtained by the same method as in Example 1,except that the density at the time when the mixture was compressed waschanged to 1.2 g/cm³.

[Production of Lithium Ion Secondary Battery]

A lithium ion secondary battery for evaluation was produced by the samemethod as in Example 1. As the electrolytic solution, a solution wasused which was prepared by adding 1% by mass of vinylene carbonate (VC)with respect to the total amount of the following mixed solution, and0.2% by mass (based on total amount of electrolytic solution) of theabove compound A, into the mixed solution which contained ethylenecarbonate containing 1 mol/L of LiPF₆, dimethyl carbonate and diethylcarbonate.

Example 6

A lithium ion secondary battery was produced in the same manner as inExample 5, except that the content of the compound A in Example 5 waschanged to 0.5% by mass based on the total amount of the electrolyticsolution.

Comparative Example 4

A lithium ion secondary battery was produced in the same manner as inExample 5, except that the compound A was not used in Example 5.

[Initial Charge/Discharge]

Each of the secondary batteries of Examples 5 to 6 and ComparativeExample 4 was subjected to the initial charge/discharge by the samemethod as the method in Example 1 and Comparative Example 1, except thatthe final voltage of the constant current discharge was set at 2.7 V.

[Resistance Measurement by AC Impedance Measurement (Upper Limit Voltageof 4.2 V)]

After the initial charge/discharge, the resistances of the lithium ionsecondary batteries of Examples 5 to 6 and Comparative Example 4 wereevaluated by the AC impedance measurement. The produced lithium ionbatteries were subjected to the constant current charge at a currentvalue of 0.2 C up to the upper limit voltage of 4.2 V in an environmentof 25° C., and were each subsequently subjected to the constant-voltagecharge at 4.2 V. The charge termination condition was set at a currentvalue of 0.01 C. Resistances of these lithium ion secondary batterieswere measured with the use of an AC impedance measuring device (VSP,Bio-Logic) in a frequency range of 20 mHz to 200 kHz with an amplitudeof 10 mV in an environment of 25° C. The measurement results are shownin FIG. 6.

[Resistance Measurement by AC Impedance Measurement (Upper Limit Voltageof 4.3 V)]

For each of the secondary batteries of Example 5 and Comparative Example4, the resistance of each of the secondary batteries was measured by thesame method as the method at the time when the upper limit voltage wasset at 4.2 V, except that the upper limit voltage was set at 4.3 V. Themeasurement results are shown in FIG. 7.

Example 7

A lithium ion secondary battery was produced in the same manner as inExample 5, except that silicon oxide was further added as the negativeelectrode active material, the density at the time when the mixture wascompressed was changed to 1.6 g/cm³, and the negative electrode wasproduced, in Example 5. Mass ratios among the negative electrode activematerial, the binder and the thickening agent in the negative electrodewere set to be graphite:siliconoxide:binder:thickeningagent=92:5:1.5:1.5.

Example 8

A lithium ion secondary battery was produced in the same manner as inExample 7, except that the content of the compound A was changed to 0.5%by mass based on the total amount of the electrolytic solution, inExample 7.

Comparative Example 5

A lithium ion secondary battery was produced in the same manner as inExample 7, except that the compound A was not used in Example 7.

[Initial Charge/Discharge]

Each of the secondary batteries of Examples 7 to 8 and ComparativeExample 5 was subjected to the initial charge/discharge by the samemethod as the method in Examples 5 to 6 and Comparative Example 4.

[Resistance Measurement by AC Impedance Measurement (Upper Limit Voltageof 4.2 V)]

For each of the secondary batteries of Examples 7 to 8 and ComparativeExample 5, the resistance of each of the secondary batteries wasmeasured by the same method as the method in Examples 5 to 6 andComparative Example 4 (the method at the time when the upper limitvoltage was set at 4.2 V). The measurement results are shown in FIG. 8.

Example 9

A lithium ion secondary battery was produced in the same manner as inExample 5, except that lithium nickel cobalt manganate(LiNi_(0.5)Co_(0.2)Mn_(0.3)O₂) was used as the positive electrode activematerial, in Example 5.

Example 10

A lithium ion secondary battery was produced in the same manner as inExample 9, except that the content of the compound A in Example 9 waschanged to 0.5% by mass based on the total amount of the electrolyticsolution.

Comparative Example 6

A lithium ion secondary battery was produced in the same manner as inExample 9, except that the compound A was not used in Example 9.

[Initial Charge/Discharge]

Each of the secondary batteries of Examples 9 to 10 and ComparativeExample 6 was subjected to the initial charge/discharge by the samemethod as the method in Examples 5 to 6 and Comparative Example 4.

[Resistance Measurement by AC Impedance Measurement (Upper Limit Voltageof 4.2 V)]

For each of the secondary batteries of Examples 9 to 10 and ComparativeExample 6, the resistance of each of the secondary batteries wasmeasured by the same method as the method in Examples 5 to 6 andComparative Example 4 (the method at the time when the upper limitvoltage was set at 4.2 V). The measurement results are shown in FIG. 9.

Example 11

A lithium ion secondary battery was produced in the same manner as inExample 5, except that lithium iron phosphate (90% by mass) was used asthe positive electrode active material, the content of the binder waschanged to 5% by mass, the density at the time when the mixture wascompressed was changed to 2.0 g/cm³, and then the positive electrode wasproduced, in Example 5.

Example 12

A lithium ion secondary battery was produced in the same manner as inExample 11, except that the content of the compound A in Example 11 waschanged to 0.5% by mass based on the total amount of the electrolyticsolution.

Comparative Example 7

A lithium ion secondary battery was produced in the same manner as inExample 11, except that the compound A was not used in Example 11.

[Initial Charge/Discharge]

Each of the secondary batteries of Examples 11 to 12 and ComparativeExample 7 was subjected to the initial charge/discharge by the samemethod as the method in Examples 5 to 6 and Comparative Example 4.

[Resistance Measurement by AC Impedance Measurement (Upper Limit Voltageof 4.2 V)]

For each of the secondary batteries of Examples 11 to 12 and ComparativeExample 7, the resistance of each of the secondary batteries wasmeasured by the same method as the method in Examples 5 to 6 andComparative Example 4 (the method at the time when the upper limitvoltage was set at 4.2 V). The measurement results are shown in FIG. 10.

Example 13

[Production of Positive Electrode]

Acetylene black (AB) (5% by mass) of the electroconductive agent, and abinder (4% by mass) were sequentially added to and mixed with lithiumnickel cobalt manganate (LiNi_(0.6)Co_(0.2)Mn_(0.2)O₂, 91% by mass) of apositive electrode active material. To the obtained mixture, NMP of adispersion medium was added, the resultant mixture was kneaded, andthereby a slurry-like positive electrode mixture was prepared. Apredetermined amount of this positive electrode mixture was evenly anduniformly applied to an aluminum foil which was a positive electrodecurrent collector and had a thickness of 20 μm. After that, thedispersion medium was volatilized, then the resultant mixture wascompressed to a density of 2.8 g/cm³ by pressing, and a positiveelectrode was obtained.

[Production of Negative Electrode]

A negative electrode was obtained by the same method as in Example 1.

[Production of Lithium Ion Secondary Battery]

A lithium ion secondary battery for evaluation was produced by the samemethod as in Example 1. As the electrolytic solution, a solution wasused which was prepared by adding 1% by mass of vinylene carbonate (VC)with respect to the total amount of the following mixed solution, and0.5% by mass (based on total amount of electrolytic solution) of theabove compound A, into the mixed solution which contained ethylenecarbonate containing 1 mol/L of LiPF₆, dimethyl carbonate and diethylcarbonate.

Example 14

A lithium ion secondary battery was produced in the same manner as inExample 13, except that the content of the compound A in Example 13 waschanged to 0.2% by mass based on the total amount of the electrolyticsolution.

Comparative Example 8

A lithium ion secondary battery was produced in the same manner as inExample 13, except that the compound A was not used in Example 13.

[Initial Charge/Discharge]

Each of the secondary batteries of Examples 13 to 14 and ComparativeExample 8 was subjected to the initial charge/discharge by the samemethod as the method in Examples 5 to 6 and Comparative Example 4.

[Resistance Measurement by AC Impedance Measurement (Upper Limit Voltageof 4.2 V)]

For each of the secondary batteries of Example 13 and ComparativeExample 8, the resistance of each of the secondary batteries wasmeasured by the same method as the method in Examples 5 to 6 andComparative Example 4 (the method at the time when the upper limitvoltage was set at 4.2 V). The measurement results are shown in FIG. 11.

[Evaluation of Cycle Characteristics]

For each of the secondary batteries of Example 14 and ComparativeExample 8, the cycle characteristics were evaluated by the same methodas the evaluation method in Example 2 and Comparative Examples 2 to 3.The discharge capacity after the charge/discharge in the first cycle inComparative Example 8 was determined to be 1, and relative values of thedischarge capacities (ratio of discharge capacity) in Example 14 andComparative Example 8 in each cycle were determined. FIG. 12 shows therelationship between the number of cycles and the relative values of thedischarge capacities. The ratio of discharge capacity after 200 cyclesin Example 14 is higher than the ratio of discharge capacity after the200 cycles in Comparative Example 8, and it is understood that Example14 is excellent in the cycle characteristics as compared withComparative Example 8.

[Evaluation of Discharge Rate Characteristics]

For each of the secondary batteries of Example 13 and ComparativeExample 8, the output characteristics of the lithium ion secondarybattery after the evaluation of the cycle characteristics were evaluatedby the method shown below. A constant current charge of 0.2 C wasperformed up to the upper limit voltage of 4.2 V, and then aconstant-voltage charge was performed at 4.2 V. The charge terminationcondition was set at a current value of 0.02 C. After that, the constantcurrent discharge was performed at a current value of 0.2 C to a finalvoltage of 2.5 V, and the capacity at the time of this discharge wasdetermined to be the discharge capacity at the current value of 0.2 C.Next, the constant current charge of 0.2 C was performed up to the upperlimit voltage of 4.2 V, subsequently the constant-voltage charge wasperformed at 4.2 V (where the charge termination condition was set atthe current value of 0.02 C), then the constant current discharge wasperformed at a current value of 0.5 C to the final voltage of 2.5 V, andthe capacity at the time of this discharge was determined to be thedischarge capacity at the current value of 0.5 C. The dischargecapacities of 1 C and 2 C were evaluated from similar charge/discharge.The output characteristics were computed by the following expression.The evaluation results of Example 13 and Comparative Example 8 are shownin FIG. 13.

Discharge capacity retention rate (%)=(discharge capacity at currentvalues of 0.2 C, 0.5 C, 1 C or 2 C/discharge capacity at current valueof 0.2 C)×100

Example 15

[Production of Positive Electrode]

Acetylene black (AB) (3% by mass) of the electroconductive agent and abinder (2% by mass) were sequentially added to and mixed with lithiumnickel cobalt aluminate (95% by mass) of the positive electrode activematerial. To the obtained mixture, NMP of a dispersion medium was added,the resultant mixture was kneaded, and thereby a slurry-like positiveelectrode mixture was prepared. A predetermined amount of this positiveelectrode mixture was evenly and uniformly applied to an aluminum foilwhich was a positive electrode current collector and had a thickness of20 μm. After that, the dispersion medium was volatilized, then theresultant mixture was compressed to a density of 3.0 g/cm³ by pressing,and a positive electrode was obtained.

[Production of Negative Electrode]

A negative electrode was obtained by the same method as in Example 1.

[Production of Lithium Ion Secondary Battery]

A lithium ion secondary battery for evaluation was produced by the samemethod as in Example 1. As the electrolytic solution, a solution wasused which was prepared by adding 1% by mass of vinylene carbonate (VC)with respect to the total amount of the following mixed solution, and0.1% by mass (based on total amount of electrolytic solution) of theabove compound A, into the mixed solution which contained ethylenecarbonate containing 1 mol/L of LiPF₆, dimethyl carbonate and diethylcarbonate.

Comparative Example 9

A lithium ion secondary battery was produced in the same manner as inExample 13, except that the compound A was not used in Example 15.

Comparative Example 10

A lithium ion secondary battery was produced in the same manner as inExample 15, except that 0.5% by mass of FEC in place of the compound Ain Example 15 was added based on the total amount of the electrolyticsolution.

[Initial Charge/Discharge]

Each of the secondary batteries of Example 15 and Comparative Examples 9to 10 was subjected to the initial charge/discharge by the same methodas the method in Examples 5 to 6 and Comparative Example 4.

[Resistance Measurement by AC Impedance Measurement (Upper Limit Voltageof 4.2 V)]

For each of the secondary batteries of Example 15 and ComparativeExamples 9 to 10, the resistance of each of the secondary batteries wasmeasured by the same method as the method in Examples 5 to 6 andComparative Example 4 (the method at the time when the upper limitvoltage was set at 4.2 V). The measurement results are shown in FIG. 14.

[Measurement of Amount of Volume Change]

Each of the secondary batteries of Example 15 and Comparative Examples 9to 10 was stored at 80° C. for 7 days. The volumes of the secondarybatteries were measured every day with an electronic densimeter based onthe Archimedes method (Electronic Densimeter MDS-300, manufactured byAlfa Mirage Co. Ltd.), and the differences from the volumes of thesecondary batteries before storage (day 0) were determined,respectively. The results are shown in FIG. 15.

As shown in FIGS. 6 to 11 and 14, even in the case where lithium nickelcobalt manganate, lithium iron phosphate or lithium nickel cobaltaluminate was used as the positive electrode active material, theresistances of the lithium ion secondary batteries of Examples 5 to 13and 15 were low to which the electrolytic solution containing apredetermined amount of the compound A was applied, as compared with thelithium ion secondary batteries of Comparative Examples 4 to 9 to whichthe electrolytic solution containing no compound A was applied. Thismechanism is not necessarily clear, but the reason is considered to bebecause similarly to the case where lithium cobaltate was used as thepositive electrode active material, the film was formed by the additionof the compound A, which was stable on the positive or negativeelectrode and of which the ion-conductivity was satisfactory, andbecause by the interaction between the compound A and the lithium ion,the lithium salt (LIPF₆) was stabilized, or activation energy fordesolvation of lithium decreased.

REFERENCE SIGNS LIST

1 . . . Non-aqueous electrolytic solution secondary battery(electrochemical device), 6 . . . Positive electrode, 7 . . . Separator,8 . . . Negative electrode.

1: An electrolytic solution comprising a compound represented by the following formula (1), wherein a content of the compound is 10% by mass or less based on a total amount of the electrolytic solution,

wherein R¹ to R³ each independently represent an alkyl group or a fluorine atom, R⁴ represents an alkylene group, and R⁵ represents an organic group containing a nitrogen atom. 2: The electrolytic solution according to claim 1, wherein R⁵ is a group represented by the following formula (2):

wherein R⁶ and R⁷ each independently represent a hydrogen atom or an alkyl group, and * represents a bond. 3: The electrolytic solution according to claim 1, wherein at least one of R¹ to R³ is a fluorine atom. 4: An electrochemical device comprising: a positive electrode; a negative electrode; and the electrolytic solution according to claim
 1. 5: The electrochemical device according to claim 4, wherein the negative electrode comprises a carbon material. 6: The electrochemical device according to claim 5, wherein the carbon material comprises graphite. 7: The electrochemical device according to claim 5, wherein the negative electrode further comprises a material comprising at least one element of the group consisting of silicon and tin. 8: The electrochemical device according to claim 4, wherein the electrochemical device is a non-aqueous electrolytic solution secondary battery or a capacitor. 